Abstract: Motors’ negative sequence（NS） current calculation and its harms for motors under various operation conditions are analyzed.Allowance time of NS current appeared under different operational conditions are roughly calculated.Relationship between positive sequence current and NS current,and relationship between positive sequence current and NS power direction are also analyzed.Problems existing in frequently used settings for blocking NS overcurrent without involving NS power direction are pointed out and it is easy to cause mal-operation when off-site asymmetric short-circuit fault occurs.Proper settings calculation methods for different NS overcurrent protection acting criteria and different protection functions are given.Satisfactory protection function can be obtained for the stator windings two-phase short-circuit of high-voltage motors by adopting NS overcurrent protection with NS power direction blocking as the auxiliary protection for the stator windings two-phase short-circuit of the high-voltage motors.